138 Uncertainty Principle
Measuring things can change them, often making the results and subsequent measurements invalid.
• Measuring sensitive variables in a system can alter them, undermining the validity of the results and the instrument of measure.
• For example, event logging in computers increases the visibility of how the computer is performing, but it also consumes computing resources, which interferes with the performance being measured.
• The uncertainty introduced by a measure is a function of the sensitivity of variables in a system and the invasiveness of the measure. Beware using invasive measures, for they can permanently alter system behaviors and lead to unintended consequences.
• Use minimally invasive measures of performance ...
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